摘要:

A standing wave phenomenon associated with outfalls is examined practically and analytically. The theory of jets is used to predict the wavelength. An extension of a theory for hydraulic jumps leads to predictions of the wave amplitude and the condition for wave breaking.

ISSN:0022-1686    

DOI:10.1080/00221689609498493

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The influence of coastal structures on coast's water quality is the subject of the present paper. Water exchange in the space between groins due to breaking wave induced currents is studied by experiments, numerical and hydraulic modelling. The results give the possibility to estimate the water quality for the area of the coastal zone, enclosed by the shoreline and the pair of shore-normal groins. That may be considered as an example of estimation of the effect of typical shore structures on the water quality.

ISSN:0022-1686    

DOI:10.1080/00221689609498494

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The unsteady wall shear stress in accelerating and decelerating turbulent flows of water in a smooth pipe was measured using two different approaches simultaneously : a “direct” mechanical approach, and a more conventional “indirect” approach involving measurement of the transient pressure gradient. The measurements covered a Reynolds number range of between 40,000 to 130,000, and values of acceleration parameter (φ) from -2 to 3. The results showed a surprising trend for the unsteady wall friction to increase in decelerating, and decrease in accelerating flows, contradicting all existing observations. It is possible that the phenomenon of relaminarisation occurring during flow acceleration could have accounted for the reduction in wall shear stress. Based on the test measurements, empirical equations for the unsteady friction factor in terms of the acceleration parameter (φ) are derived. Limiting values of (φ) within which the flow may be approximated as being quasi-steady are also proposed.

ISSN:0022-1686    

DOI:10.1080/00221689609498495

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

divers typically exhibit a tendency for grain size to become finer in the downstream direction. Data for a set of large-scale experiments on the aggradation of heterogeneous gravel have recently become available. These experiments show substantial downstream fining over several tens of meters. Here a decoupled numerical Tiodel for bed aggradation and downstream fining is developed in an attempt to test an existing gravel ransport model against the experimental data. Generally good agreement is found between the predictions and he observations in the absence of all but trivial adjustments to the gravel transport model. The same transport elation does not perform as well for a corresponding case of uniform sediment. In all of the experiments the Froude number was close to unity, a condition which would suggest that a decoupled model might break iown. Coupled and decoupled models for uniform sediment are thus compared for a case with Froude number very close to unity. They are also compared for cases in which the upstream water discharge, sediment feed rate and downstream water surface elevation vary strongly. The surprisingly good agreement between the two nodels suggests that concerns in the literature about the use of decoupled models may have been overstated.

ISSN:0022-1686    

DOI:10.1080/00221689609498496

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Meandering channels typically deposit sediments near their inner bank to form point bars. Laboratory experiments with narrow sharp bends show that under identical flow conditions the configuration of point bars depends on particle size. Explanation to this grain-size effect is found in a three-dimensional particle stability. Despite favorable secondary currents, coarse grains tend to move toward the thalweg and coarse-grained point bar deposits are eroded as the side-slope angle approaches the angle of repose of the bed material. Calculated results coincide with experimental observations. Point bars are considerably smaller for coarse-sand deposits than fine sands.

ISSN:0022-1686    

DOI:10.1080/00221689609498497

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The mathematical model for simulating suspended sediment transport under equilibrium and non-equilibrium situations is described. Using the hydrodynamic variable field obtained from a refined turbulent free surface flow model, the suspension transport model involves bed boundary conditions for either the sediment flux to or from the bed, or an estimated concentration level, which are tested. The Schmidt number variability is also studied for several particle types. Some 2D vertical test cases for equilibrium situations or non-equilibrium situations with net erosion or net deposition flux to the bed are presented, and the predicted development of the concentration profiles is compared with measurements.

ISSN:0022-1686    

DOI:10.1080/00221689609498498

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The control of reservoir sedimentation through hydraulic flushing has been employed in several parts of the world to sustain the useful storage capacity of the reservoirs. However, no comprehensive analysis has been conducted to understand the sediment flushing processes. In this study, laboratory experiments were performed to investigate the flushing processes during drawdown flushing, including outflow sediment discharge, characteristics of the flushing channel and flushing effectiveness. From both laboratory and field data, it is found that outflow sediment discharge can be well related to a hydrauic parameter which is a function of outlet discharge, water-surface gradient and flushing channel width. It is also found that flushing efficiency increases dramatically when retrogressive erosion emerges. A geomorphic relationship is used to estimate the equilibrium width of the flushing channel. A 1-D diffusion model presented herein is employed only to simulate the general trend of bed profile evolution and the amount of reservoir sediment removal during flushing in order to evaluate the applicabilities and limitations of this model. Simulated results of this diffusion model agree well with laboratory data in a narrow flume (with essentially 1-D flow) with nearly uniform flow condition after rapid drawdown operation. However, there is a 15% average error if this diffusion model is applied to a wide reservoir (relative to the width of the flushing outlet) as performed in our laboratory. A two-dimensional or three-dimensional model is needed to study flushing processes involving strong lateral erosion in a wide reservoir.

ISSN:0022-1686    

DOI:10.1080/00221689609498499

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

HYDRODYNAMIQUE - Une Introductionby Walter H. Graf and M. S. Altinakar, Presses Poly techniques et Universitaires Romandes, Lausanne, 1995

ISSN:0022-1686    

DOI:10.1080/00221689609498500

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

IMPROVED PREDICTION OF BENDING PLUMESFrick, W.E., Baumgartner, D.J. and Fox, C.G., Journal of Hydraulic Research, Vol. 32, No. 6, 1994, pp. 935-950

ISSN:0022-1686    

DOI:10.1080/00221689609498501

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

TURBULENT FLOW IN SMOOTH-WALL OPEN-CHANNELS WITH DIFFERENT SLOPEby Li Xingyu, Dong Zengnan and Chen Changzhi, Journal of Hydraulic Research, Vol. 33, No. 3, 1995, pp. 333-348

ISSN:0022-1686    

DOI:10.1080/00221689609498502

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor